Alan Mathison Turing,
OBE,
FRS ( , ; 23 June 1912 – 7 June
1954), was an
English mathematician,
logician,
cryptanalyst,
and
computer scientist. He was
influential in the development of
computer science and providing a
formalisation of the concept of the
algorithm and computation with the
Turing machine. In 1999,
Time Magazine named Turing as one of
the
100 Most
Important People of the 20th Century for his role in the
creation of the modern
computer, and
stated: "The fact remains that everyone who taps at a keyboard,
opening a spreadsheet or a word-processing program, is working on
an incarnation of a Turing machine."In 2002, Turing was ranked
twenty-first on the
BBC nationwide poll
of the
100 Greatest Britons.
His
Turing test was a significant and
characteristically provocative contribution to the debate regarding
artificial
intelligence.
During
the Second World War, Turing worked for
the Government Code and Cypher
School at Bletchley
Park, Britain's codebreaking centre. For a time he was
head of
Hut 8, the section responsible for
German naval
cryptanalysis. He devised
a number of techniques for breaking German
ciphers, including the method of the
bombe, an
electromechanical machine that could find
settings for the
Enigma machine.
After the
war he worked at the National Physical Laboratory, where he created one of the first designs for a
stored-program computer, the ACE.
Towards the end of his life Turing became interested in
chemistry. He wrote a paper on the chemical basis
of
morphogenesis, and he predicted
oscillating chemical reactions such as the
Belousov–Zhabotinsky
reaction, which were first observed in the 1960s.
Turing's
homosexuality resulted in a
criminal prosecution in 1952—homosexual acts were illegal in the
United Kingdom at that time—and he accepted treatment with female
hormones,
chemical castration,
as an alternative to prison. He died in 1954, several weeks before
his 42nd birthday, from an apparently self-administered
cyanide poisoning, although his mother (and some
others) considered his death to be accidental.
On 10 September
2009, following an Internet campaign, British Prime Minister Gordon
Brown made an official public apology on behalf of the British
government for the way in which Turing was treated after the
war.
Childhood and youth
Alan
Turing was conceived in Chhatrapur, Orissa, India. His father, Julius Mathison
Turing, was a member of the
Indian
Civil Service.
Julius and wife Sara (née Stoney; 1881–1976,
daughter of Edward Waller Stoney, chief engineer of the Madras
Railways) wanted Alan to be brought up in England, so they returned
to Maida
Vale, London, where Alan Turing was born on 23 June
1912, as recorded by a blue plaque on
the outside of the building, now the Colonnade
Hotel. He had an elder brother, John.
His father's civil
service commission was still active, and during Turing's childhood
years his parents travelled between Guildford, England and India, leaving their two sons to stay
with friends in Hastings in England. Very early in life, Turing
showed signs of the genius he was to display more prominently
later.
His parents enrolled him at St Michael's, a day school, at the age
of six. The headmistress recognised his talent early on, as did
many of his subsequent educators.
In 1926, at the age of 14, he went on to
Sherborne
School, a famous and expensive public school in Dorset.
His first
day of term coincided with the General Strike in
Britain, but so determined was he to attend his first day that he
rode his bicycle unaccompanied more than from Southampton to school, stopping overnight at an
inn.
The computer room at King's College,
Cambridge is now named after Turing, who became a student there in
1931 and a Fellow in 1935
Turing's natural inclination toward mathematics and science did not
earn him respect with some of the teachers at Sherborne, whose
definition of education placed more emphasis on the
classics. His headmaster wrote to his parents: "I
hope he will not fall between two stools. If he is to stay at
Public School, he must aim at becoming
educated. If he is
to be solely a
Scientific Specialist, he is wasting his
time at a Public School". Despite this, Turing continued to show
remarkable ability in the studies he loved, solving advanced
problems in 1927 without having even studied elementary
calculus. In 1928, aged 16, Turing encountered
Albert Einstein's work; not only did
he grasp it, but he extrapolated Einstein's questioning of
Newton's laws of motion from a text
in which this was never made explicit.
Turing's hopes and ambitions at school were raised by the close
friendship he developed with a slightly older fellow student,
Christopher Morcom, who was
Turing's first love interest. Morcom died suddenly only a few weeks
into their last term at Sherborne, from complications of
bovine tuberculosis, contracted after
drinking infected cow's milk as a boy. Turing's religious faith was
shattered and he became an atheist. He adopted the conviction that
all phenomena, including the workings of the human brain, must be
materialistic.
University and work on computability
Turing's
unwillingness to work as hard on his classical studies as on
science and mathematics caused him to fail to win a scholarship to
Trinity
College, Cambridge, and he went on to the college of his second
choice, King's
College, Cambridge. He was an undergraduate there from 1931 to
1934, graduating with a first class honours degree, and in 1935 was
elected a fellow at King's on the strength of a dissertation on the
central limit theorem.
In his momentous paper "On Computable Numbers, with an Application
to the
Entscheidungsproblem" (submitted
on 28 May 1936), Turing reformulated
Kurt Gödel's 1931 results on the limits of
proof and computation, replacing Gödel's universal arithmetic-based
formal language with what are now called
Turing machines, formal and simple devices.
He proved that some such machine would be capable of performing any
conceivable mathematical computation if it were representable as an
algorithm.
Turing machines are to this day the central object of study in
theory of computation. He went on to
prove that there was no solution to the
Entscheidungsproblem by first showing that the
halting problem for Turing machines is
undecidable: it is not possible to
decide, in general, algorithmically whether a given Turing machine
will ever halt. While his proof was published subsequent to
Alonzo Church's equivalent proof in
respect to his
lambda calculus,
Turing's work is considerably more accessible and intuitive. It was
also novel in its notion of a 'Universal (Turing) Machine', the
idea that such a machine could perform the tasks of any other
machine. "Universal" in this context means what is now called
programmable. The paper also introduces the notion of
definable numbers.
From
September 1936 to July 1938 he spent most of his time at the
Institute
for Advanced Study, Princeton University, studying under Alonzo
Church. As well as his pure mathematical work, he
studied cryptology and also built three of four stages of an
electro-mechanical binary multiplier. In June 1938 he obtained his
Ph.D. from Princeton; his
dissertation introduced the notion of relative computing, where
Turing machines are augmented with so-called
oracles, allowing a study of problems that
cannot be solved by a Turing machine.
Back in Cambridge, he attended lectures by
Ludwig Wittgenstein about the
foundations of mathematics. The
two argued and disagreed, with Turing defending
formalism and
Wittgenstein arguing that mathematics does not discover any
absolute truths but rather invents them.
He also started to
work part-time with the Government Code and Cypher School
.
Cryptanalysis
During
the Second World War, Turing was a main
participant in the efforts at Bletchley Park to break German
ciphers. Building on cryptanalysis work carried out
in Poland by Marian Rejewski, Jerzy Różycki and Henryk Zygalski from Cipher Bureau before the war, he contributed
several insights into breaking both the Enigma machine and the Lorenz SZ 40/42 (a Teletype cipher attachment codenamed "Tunny" by the
British), and was, for a time, head of Hut 8,
the section responsible for reading German naval
signals.
Since
September 1938, Turing had been working part-time for the Government
Code and Cypher School (GCCS), the British code breaking
organisation. He worked on the problem of the German
Enigma machine, and collaborated with Dilly
Knox, a senior GCCS codebreaker. On 4 September 1939, the day
after the UK declared war on Germany, Turing reported to Bletchley
Park, the wartime station of GCCS.
Turing–Welchman bombe
Within weeks of arriving at Bletchley Park, Turing had specified an
electromechanical machine which could help break Enigma faster than
bomba from 1932, the
bombe, named after and building upon the original
Polish-designed bomba. The bombe, with an enhancement suggested by
mathematician
Gordon Welchman,
became one of the primary tools, and the major automated one, used
to attack Enigma-protected message traffic.
Professor
Jack Good, cryptanalyst working
at the time with Turing at Bletchley Park, later said: "Turing's
most important contribution, I
think, was of part of the
design of the bombe, the cryptanalytic machine. He had the idea
that you could use, in effect, a theorem in logic which sounds to
the untrained ear rather absurd; namely that from a contradiction,
you can deduce
everything."
The bombe searched for possibly correct settings used for an Enigma
message (i.e., rotor order, rotor settings, etc.), and used a
suitable "
crib": a fragment of
probable
plaintext. For each possible
setting of the rotors (which had of the order of 10
^{19}
states, or 10
^{22} for the U-boat Enigmas which eventually
had four rotors, compared with the usual Enigma variant's three),
the bombe performed a chain of logical deductions based on the
crib, implemented electrically. The bombe detected when a
contradiction had occurred, and ruled out that setting, moving onto
the next. Most of the possible settings would cause contradictions
and be discarded, leaving only a few to be investigated in detail.
Turing's bombe was first installed on 18 March 1940. Over two
hundred bombes were in operation by the end of the war.
Hut 8 and Naval Enigma
In December 1940, Turing solved the
naval Enigma
indicator
system, which was more mathematically complex than the indicator
systems used by the other services. Turing also invented a
Bayesian statistical technique termed
"
Banburismus" to assist in breaking
naval Enigma. Banburismus could rule out certain orders of the
Enigma rotors, reducing time needed to test settings on the bombes.
In 1941, Turing proposed marriage to Hut 8 co-worker Joan Clarke, a
fellow mathematician, but their engagement was short-lived. After
admitting his homosexuality to his fiancée, who was reportedly
"unfazed" by the revelation, Turing decided that he could not go
through with the marriage.
In July 1942, Turing devised a technique termed
Turingismus or
Turingery for use against the
Lorenz cipher used in the Germans' new Geheimschreiber machine
("secret writer") which was one of those codenamed "Fish". He also
introduced the Fish team to
Tommy
Flowers who, under the guidance of
Max
Newman, went on to build the
Colossus computer, the world's first
programmable digital electronic computer, which replaced simpler
prior machines (including the "
Heath Robinson") and
whose superior speed allowed the brute-force decryption techniques
to be applied usefully to the daily changing cyphers.
A frequent misconception is that Turing was a key figure in the design of Colossus; this was not the case. While working at Bletchley, Turing, a talented long-distance runner, occasionally ran the to London when he was needed for high-level meetings.
Turing travelled to the United States in November 1942 and worked
with U.S.
Navy cryptanalysts on Naval Enigma and bombe
construction in Washington, and assisted at Bell Labs with the development of secure speech devices. He returned to
Bletchley Park in March 1943. During his absence,
Hugh Alexander had officially
assumed the position of head of Hut 8, although Alexander had been
de facto head for some time—Turing having little interest
in the day-to-day running of the section. Turing became a general
consultant for cryptanalysis at Bletchley Park.
In the latter part of the war he moved to work at
Hanslope Park, where he further
developed his knowledge of electronics with the assistance of
engineer Donald Bailey. Together they undertook the design and
construction of a portable
secure voice
communications machine codenamed
Delilah. It was intended for
different applications, lacking capability for use with
long-distance radio transmissions, and in any case, Delilah was
completed too late to be used during the war. Though Turing
demonstrated it to officials by encrypting/decrypting a recording
of a
Winston Churchill speech,
Delilah was not adopted for use.
In 1945, Turing was awarded the
OBE for his wartime services,
but his work remained secret for many years. A biography published
by the Royal Society shortly after his death recorded:
Early computers and the Turing test
From 1945
to 1947 he was at the National Physical Laboratory, where he worked on the design of the ACE (Automatic Computing Engine). He
presented a paper on 19 February 1946, which was the first detailed
design of a
stored-program
computer. Although ACE was a feasible design, the secrecy
surrounding the wartime work at Bletchley Park led to delays in
starting the project and he became disillusioned. In late 1947 he
returned to Cambridge for a sabbatical year. While he was at
Cambridge, the
Pilot ACE was built in his
absence. It executed its first program on 10 May 1950.
In 1948
he was appointed Reader in
the Mathematics Department at Manchester. In 1949
he became deputy director of the computing laboratory at the
University of
Manchester, and worked on software for one of the earliest
stored-program
computers—the
Manchester Mark 1.
During this time he continued to do more abstract work, and in
"
Computing
machinery and intelligence" (Mind, October 1950), Turing
addressed the problem of
artificial intelligence, and
proposed an experiment now known as the
Turing test, an attempt to define a standard for
a machine to be called "intelligent". The idea was that a computer
could be said to "think" if it could fool an interrogator into
thinking that the conversation was with a human. In the paper,
Turing suggested that rather than building a program to simulate
the adult mind, it would be better rather to produce a simpler one
to simulate a child's mind and then to subject it to a course of
education.
In 1948, Turing, working with his former undergraduate colleague,
D. G. Champernowne, began writing a
chess program for a computer that did not yet exist.
In 1952, lacking a computer powerful enough to execute the program,
Turing played a game in which he simulated the computer, taking
about half an hour per move. The game was recorded. The program
lost to Turing's colleague
Alick
Glennie, although it is said that it won a game against
Champernowne's wife.
Pattern formation and mathematical biology
Turing worked from 1952 until his death in 1954 on
mathematical biology, specifically
morphogenesis. He published one paper
on the subject called "The Chemical Basis of Morphogenesis" in
1952, putting forth the Turing hypothesis of pattern formation. His
central interest in the field was understanding
Fibonacci phyllotaxis, the existence of
Fibonacci numbers in plant structures. He
used
reaction–diffusion
equations which are now central to the field of
pattern formation. Later papers went
unpublished until 1992 when
Collected Works of A.M.
Turing was published.
Conviction for gross indecency
In January 1952 Turing picked up 19-year-old Arnold Murray outside
a cinema in Manchester. After a lunch date, Turing invited Murray
to spend the weekend with him at his house, an invitation which
Murray accepted although he did not show up. The pair met again in
Manchester the following Monday, when Murray agreed to accompany
Turing to the latter's house. A few weeks later Murray visited
Turing's house again, and apparently spent the night there.
After Murray helped an accomplice to break into his house, Turing
reported the crime to the police. During the investigation, Turing
acknowledged a sexual relationship with Murray.
Homosexual acts were illegal in the United
Kingdom at that time, and so both were charged with gross indecency
under
Section
11 of the
Criminal
Law Amendment Act 1885, the same crime that
Oscar Wilde had been convicted of more than
fifty years earlier.
Turing was given a choice between imprisonment or probation
conditional on his agreement to undergo
hormonal treatment designed to reduce
libido. He accepted
chemical castration via
oestrogen hormone injections, one of the side
effects of which was that he grew breasts.
Turing's
conviction led to the removal of his security clearance, and barred
him from continuing with his cryptographic consultancy for GCHQ.
At the
time, there was acute public anxiety about spies and homosexual
entrapment by Soviet agents, due to the recent exposure of the
first two members of the Cambridge
Five, Guy Burgess and Donald Maclean, as KGB double agents. Turing was never
accused of espionage but, as with all who
had worked at Bletchley
Park, was prevented from discussing his war
work.
Death
On 8 June 1954, Turing's cleaner found him dead; he had died the
previous day. A
post-mortem examination
established that the cause of death was cyanide poisoning. When his
body was discovered an apple lay half-eaten beside his bed, and
although the apple was not tested for cyanide, it is speculated
that this was the means by which a fatal dose was delivered.
An
inquest determined that he had committed suicide, and he was
cremated at Woking crematorium
on 12 June 1954.
Turing's mother argued strenuously that the ingestion was
accidental, caused by her son's careless storage of laboratory
chemicals. Biographer
Andrew Hodges
suggests that Turing may have killed himself in an ambiguous way
quite deliberately, to give his mother some
plausible deniability. Others suggest
that Turing was re-enacting a scene from the 1938 film
Snow White, his favourite
fairy tale, pointing out that he took "an
especially keen pleasure in the scene where the Wicked Witch
immerses her apple in the poisonous brew."
Epitaph
Legacy
Since 1966, the
Turing Award has been
given annually by the
Association for Computing
Machinery to a person for technical contributions to the
computing community. It is widely considered to be the computing
world's highest honor, equivalent to the
Nobel Prize.
Breaking the Code is a
1986 play by
Hugh Whitemore about
Alan Turing.
The play ran in London's West End beginning in November 1986 and on Broadway from 15 November 1987 to 10 April 1988.
There was also a 1996
BBC television production.
In all cases,
Derek Jacobi played
Turing. The Broadway production was nominated for three
Tony Awards including Best Actor in a Play, Best
Featured Actor in a Play, and Best Direction of a Play, and for two
Drama Desk Awards, for Best Actor
and Best Featured Actor. Turing was one of four mathematicians
examined in the 2008
BBC documentary entitled
"Dangerous Knowledge".
On 23 June 1998, on what would have been Turing's 86th birthday,
Andrew Hodges, his biographer,
unveiled an official
English
Heritage Blue Plaque at his
birthplace and childhood home in Warrington Crescent, London, now
the Colonnade hotel.
To mark the 50th anniversary of his death, a
memorial plaque was unveiled on 7 June 2004 at his former
residence, Hollymeade, in Wilmslow, Cheshire.
On 13
March 2000, Saint Vincent and the
Grenadines issued a set of stamps
to celebrate the greatest achievements of the twentieth century,
one of which carries a recognisable portrait of Turing against a
background of repeated 0s and 1s, and is captioned: "1937: Alan
Turing's theory of digital computing".
On 28
October 2004, a bronze statue of Alan Turing sculpted by John W Mills was unveiled at the University
of Surrey in Guildford, marking the 50th anniversary of
Turing's death; it portrays him carrying his books across the
campus.
In 2006,
Boston Pride named Turing their
Honorary Grand Marshal.
A 1.5-ton, life-size statue of Turing was unveiled on 19 June 2007
at Bletchley Park. Built from approximately half a million pieces
of Welsh
slate, it was sculpted by
Stephen Kettle, having been commissioned by
the late American billionaire
Sidney
Frank.
Turing has been honored in various ways in Manchester, the city
where he worked towards the end of his life.
In 1994, a stretch of
the A6010 road (the Manchester city intermediate ring road) was named Alan Turing
Way. A bridge carrying this road was widened, and carries
the name Alan Turing Bridge.
A statue of Turing was unveiled in Manchester on 23 June 2001. It is in Sackville
Park, between the University of Manchester building on Whitworth Street and the Canal
Street gay village. The
memorial statue, depicts the "father of modern computing" sitting
on a bench at a central position in the park. The statue was
unveiled on Turing's birthday.
Turing is shown holding an apple—a
symbol classically used to represent forbidden love, as well as
being the fruit of the tree of knowledge, the object that inspired
Isaac Newton's theory of gravitation
and the means of Turing’s own death. The cast bronze bench carries
in relief the text 'Alan Mathison Turing 1912–1954', and the motto
'Founder of Computer Science' as it would appear if encoded by an
Enigma machine: 'IEKYF ROMSI ADXUO
KVKZC GUBJ'.
A plinth at the statue’s feet says ‘Father of computer science,
mathematician, logician, wartime codebreaker, victim of prejudice’.
There is also a
Bertrand Russell
quotation saying ‘Mathematics, rightly viewed, possesses not only
truth, but supreme beauty – a beauty cold and austere, like that of
sculpture.’ The sculptor buried his old
Amstrad computer, which was an early popular home
computer, under the plinth, as a tribute to "the godfather of all
modern computers".
In August 2009,
John
Graham-Cumming started a petition urging the British Government
to posthumously apologise to Alan Turing for prosecuting him as a
homosexual. The petition received thousands of signatures. Prime
Minister
Gordon Brown acknowledged the
petition, releasing a statement on 10 September 2009 apologising
and describing Turing's treatment as "appalling":
Thousands of people have come together to demand
justice for Alan Turing and recognition of the appalling way he was
treated. While Turing was dealt with under the law of the time and
we can't put the clock back, his treatment was of course utterly
unfair and I am pleased to have the chance to say how deeply sorry
I and we all are for what happened to him. [...] So on behalf of
the British government, and all those who live freely thanks to
Alan's work I am very proud to say: we're sorry, you deserved so
much better.
Tributes by universities
A celebration of Turing's life and
achievements arranged by the
British Logic Colloquium and the
British
Society for the History of Mathematics was held on 5 June 2004
at the
University of
Manchester; the
Alan Turing
Institute was initiated in the university that summer.
The
building housing the School of Mathematics, the Photon Science Institute, and the Jodrell Bank Centre for
Astrophysics is named the Alan Turing Building and was opened in July 2007.
In culture
An
urban legend holds that the logo of
Apple
computers is a
tribute to Alan Turing, with the bite mark a reference to his
method of suicide, something that the company denies.
The
Turing Relay is a six-stage relay race on riverside footpaths from
Ely to Cambridge and back. These paths were used
for running by Turing while at Cambridge; his
marathon best time was 2 hours,
46 minutes, while the marathon world best time in the early
1940s was around 2 hours, 25 minutes.
See also
References
Further reading
- Levin, Janna (2006). A Madman Dreams of Turing
Machines. New York, New
York: Knopf. ISBN
978-1400032402
- Agar, Jon (2002). The Government Machine. Cambridge, Massachusetts: The MIT Press.
ISBN 0-262-01202-2
- Beniger, James (1986). The Control Revolution:
Technological and Economic Origins of the Information Society.
Cambridge, Massachusetts: Harvard
University Press. ISBN 0-674-16986-7
- Campbell-Kelly, Martin (ed.) (1994). Passages in the Life
of a Philosopher. London: William Pickering. ISBN
0-8135-2066-5
- Campbell-Kelly, Martin, and Aspray, William (1996).
Computer: A History of the Information Machine. New York:
Basic Books. ISBN 0-465-02989-2
- Ceruzzi, Paul (1998). A History of Modern Computing.
Cambridge, Massachusetts, and London: MIT
Press. ISBN 0-262-53169-0
- Chandler, Alfred (1977). The Visible Hand: The Managerial
Revolution in American Business. Cambridge, Massachusetts: Belknap Press.
ISBN 0-674-94052-0
- Edwards, Paul N (1996). The Closed World. Cambridge, Massachusetts: MIT Press. ISBN
0-262-55028-8
- Hochhuth, Rolf. Alan Turing
- Lubar, Steven (1993) Infoculture. Boston and New York: Houghton
Mifflin. ISBN 0-395-57042-5
- Petzold, Charles (2008). "The
Annotated Turing: A Guided Tour through Alan Turing's Historic
Paper on Computability and the Turing Machine". Indianapolis: Wiley Publishing. ISBN
978-0-470-22905-7
- Smith, Roger (1997). Fontana History of the Human
Sciences. London: Fontana.
- Weizenbaum, Joseph (1976). Computer Power and Human
Reason. London: W.H. Freeman. ISBN 0-7167-0463-3
- Williams, Michael R. (1985). A History of Computing
Technology. Englewood Cliffs, New
Jersey: Prentice-Hall.
ISBN 0-8186-7739-2
- Turing's mother, Sara Turing, who survived him by many years,
wrote a biography of her son glorifying his life. Published in 1959, it
could not cover his war work; scarcely 300 copies were sold (Sara
Turing to Lyn Newman, 1967, Library of St John's
College, Cambridge). The six-page foreword by Lyn Irvine includes reminiscences and is more
frequently quoted.
- Breaking the Code is a 1986 play by Hugh Whitemore, telling the story of Turing's
life and death. In the original West End and Broadway runs, Derek Jacobi
played Turing – and he recreated the role in a 1997 television film
based on the play made jointly by the BBC and
WGBH,
Boston. The play is published by Amber Lane Press,
Oxford.
ASIN: B000B7TM0Q
External links
- Papers